Testing approaches for the release of metals from ceramic articles : in support of the revision of the Ceramic Directive 84/500/EEC

The overall aim of this study was to investigate the release of metals from ceramics into food and simulants, and to develop adequate methodologies for testing these articles including at lower limits. In the present work, the release of metals from 73 ceramic samples including 2 reference materials was investigated under different conditions. The sets of samples studied aimed to represent a vast variety of articles including hand crafted and highly decorated samples more prone to release a broader range and greater levels of metals. A comparison between two simulants and a benchmark food (acetic acid 4% for 24 h at 22°C, citric acid 0.5% for 2 h at 70°C and hot tomato sauce) showed that migration was higher in either simulants than into tomato sauce (2 h at 70°C). Results also showed that the migration profile in acetic acid was more representative for the tomato sauce. It was observed that is necessary to use of at least four replicates for each migration experiment due to the heterogeneity of the samples that Pb to a large variability of data. The relationship between the third and the first migration was shown to be not always constant and most of the time higher than 10% with respect to the first migration. This implies that prediction of values for the third migration based on the value of a first migration may not be derivable. Experiments on accelerated testing showed that increasing the acidity in an attempt to substitute the first two migrations in repeat testing were not successful from lack of clear relationships of the impact of acidity on release kinetics or mechanisms for different metals. No significant difference was observed between a test protocol with daily successive migrations and one with a lag phase (e.g. two days, representing a weekend). A longer storage (representing occasionally used articles) did not affect considerably the metals release for ceramics tableware. This implies that a repeat use testing is adequate regardless of the frequency of use of tableware articles, and that testing is not subjected to start on certain days of the weeks, which means productivity can be maintained if establishing a repeat use testing. For cookware, which had a smaller sample set of six different articles, three different profiles of Pb released were observed. For two samples the release of Pb over repeat testing in acetic acid 4% (24 h at 22°C) gave much higher values than those in boiling tomato sauce (6 h). For three samples the respective releases of Pb were comparable in both media. One sample presented higher releases of Pb and Cd in tomato sauce than in acetic acid 4%.